Michigan Natural Features Inventory

MSU Extension

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Plants and Animals

Lyogyrus walkeriCanadian duskysnail

Key Characteristics

The Canadian duskyshell has an ovately conic, finely striated, tan-colored shell of about .1 inch in length, with 4 deeply sutured whorls and a large rounded aperature. The snail body is dark in color, particularly on the head.

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

Snails of the Amnicolid family, to which the Canadian duskysnail belongs, have shown significantly reduced reproductive success rate in waters with a ph below 5 and reduced calcium content, as may occur in areas affected by acid rain (Shaw and Mackie 1990). Efforts to decrease the burning of fossil fuels should therefore benefit this species and many other aquatic organisms. Herbicide/insecticide application (Kosanke et al. 1988), and other sources of heavy metal and chemical pollution should be avoided near waterbodies containing vulnerable snail species, as these often result in reproductive failure and adult fatality (Besser et al. 2007, Gomot 1998) . Major alterations to aquatic habitats in the form of dredging, impoundment or channelization should be carried out only with monitoring and mitigation measures in place to account for affected freshwater species.

Active Period

Active from first week of June to first week of October

Survey Methods

There are several effective methods for conducting aquatic snail surveys. Areas of coarse cobble substrate are best surveyed with a glass-bottomed bucket or scuba search, and hand collecting. Stones and sunken pieces of wood can be picked up, searched, and replaced. Dip net suveys are employed at soft substrate locations. Aquatic vegetation held over a bucket and vigorously shaken to remove individual snails is another technique (Groves 2007).